1. Field of the Invention
The present invention relates to an optical tomographic image photographing apparatus arranged to photograph a tomographic image of an examined object.
2. Description of Related Art
Conventionally, as an optical tomographic image photographing apparatus arranged to photograph a tomographic image of an examined object, there is known an optical coherence tomograph (OCT) using low coherent light (see Japanese Patent Application Unexamined Publication No. 2007-151622). This apparatus is used for obtaining a tomographic image of a living body part such as an eyeball and a skin, for example.
In such an optical tomographic image photographing apparatus, there is known a Fourier domain OCT arranged to obtain the tomographic image of the examined object by performing Fourier analysis on spectral information obtained by a photodetector (see Japanese Patent Application Unexamined Publication No. 2007-151622). Examples of the Fourier domain OCT include an SD-OCT using a spectral optical system as a photo-receiving optical system and an SS-OCT using a variable wave-length light source as a projection optical system.
In a tomographic image which is obtained by an interference optical system based on the Fourier domain OCT, visibility (interference visibility) is highest at a depth position at which the optical path length of measurement light and the optical path length of reference light become equal and is lowered with distance from the depth position. Therefore, an image with high visibility and high resolution is obtained in the vicinity of the depth position. However, an image with low visibility and low resolution is obtained in a portion far from the depth position. Accordingly, a portion an examinee desires to observe could be unobservable.